Opposed piston cutting apparatus



July 6, 1965 w. L. TENNEY OPPOSED PISTON CUTTING APPARATUS 2Sheets-Sheet 1 F'ilecl June 29, 1961 mm mm Mn L M m M W ATTORNEYS y 1965w. TENNEY 3,192,972

OPPOSED PISTON CUTTING APPARATUS Filed June 29. 1961 2 Sheets-Sheet 2INVEN TOR.

WILLIAM L. TENNEY ATTORNEYS United States Patent l 3,192,?72 @PPOhEECUTTENG APPARATUS William L. Tenney, (Irystal ham'l vfinn. Filed June29, 1961, Ser. No. 129,696 Qlaims. (Cl. 143-63} This invention relatesto portable self-powered cutting devices, such as power saws and thelike, operated by novel internal combustion apparatus.

The present invention is particularly directed to power saws and cuttingmachines of the reciprocating blade type, which are capable of effectivecutting operation where space .is limited, and in which the motive powerfor reciprocating the cutting blades is so obtained that vibration issubstantially minimized. Thus, by utilizing two cutting bladesreciprocating side by side in parallel but opopsite directions, anddriving each of the blades respectively from one of the opposed pistonsof a dual opposed piston internal combustion engine, the masses of thepiston, and of the connected blades, will move in opposite directionsand tend to cancel the inertia efiects of each other, with a consequentsubstantial reduction in vibration.

Such a direct transmission of motive power to the blades provides abasically more efficient power transmission arrangement, since frictionlosses are minimized and the size and weight of the apparatus can besignificantly reduced. Furthermore, reaction forces generated by contactof the cutter blades against the material being cut can beself-canceling.

In this connection reference is made to copending application Serial No.791,107, filed February 4, 1959, now Patent No. 3,023,564, of which thisapplication is a continuation-in-part. In said parent application thereis disclosed a novel'internal combustion mass reaction engine in whichthe piston and cylinder members are mounted for relative movement on asupporting frame or the like, and wherein there is a direct power outputconnection from one of these members to a reciprocating cutter blade,which blade thus moves concurrently with the member by which it isdriven. The supply of fuel, i.e., a combustible fuel-air mixture in thecase of a carburetor fed engine, is accomplished, as disclosed in saidparent application, through a flexible tube extending between thecarburetor and the cylinder member. In the present invention, such aflexible connection can be eliminated. Accordingly, the primary objectof this invention is to provide a novel internal combustion engine drivefor reciprocating cutting devices, particularly saws and the like.

Another object of the invention is to provide such a drive in whichoppositely reciprocating cutting baldes are employed, and such bladesare driven respectively by opposed and oppositely moving pistons of aninternal cornbustion engine having a combustion chamber formed by acylinder and opposed pistons therein, thus substantially minimizingvibration due to reciprocation of these parts of the drive.

Another object of the invention is to provide a novel, lightweight,portable power saw having reciprocating cutters. a V

' a An additional object of the invention is to provide a .novel directdrive arrangement between a piston engin and a reciprocating cutterblade.

Other objects and advantages of the invention will be apparent from thefollowing description, the accompanying drawings and the appendedclaims.

' In'the drawings- FIG. 1 is a perspective view of a typicalconfiguration rof a'portable power saw incorporating the features of thepresent invention;

3,l2,9l2 Patented July 6, 1965 FIG. 2 is a view, partially broken away,taken on a vertical section line through the saw shown in FIG. 1;

FIG. 3 is a partial sectional view taken on line 3? of FlG. 2;

FIG. 4 is an enlarged detail sectional view taken on line 4-4 of FIG. 2;

FIGS. 5 and 6 are schematic views illustrating movement of the partsduring operation of the saw;

FIGS. 7 and 8 are schematic showings of modified engine constructions;and 7 FIGS. 9 and 16 are, respectively, front and side views showing theprinciples of the invention applied to another form of cutting machine,a reciprocating cutter bar mowing machine.

Referring to the drawing, which illustrates a preferred embodiment ofthe invention, the main body of the saw is provided by a cylinder member13 which may be cast from suitable metal or machined, as desired, andmay have cooling fins 1:. formed thereon. A pair of handles 12 aremounted on hands 13 clamped in any suitable manner around the body it}for grasping by the user to sup port and guide the device. Within thebody 19, formed with its longitudinal axis eccentric with respect totheiaxis of the body itself, is an engine cylinder is", and within thiscylinder there are opposed pistons 16 and 13, which may includeconventional sealing rings (not shown) providing the usual sliding sealbetween their outer surfaces and the walls of the engine cylinder. Thesepistons, in cooperation with the cylinder 15, define a variable volumepower cylinder which provides space Ztl for combustion and expansionofcombustible charges.

A suitable igniter, such as an ignition plug 22 is mounted to extendthrough a side wall of the cylinder 15 for the purpose of ignitingcombustible charges within the cylinder. This plug can be energized inany known manner, such as by a battery or a magneto (not shown). Thesecharges are introduced through an inlet port 24 controlled by piston 18,and products of combustion are exhausted from the cylinder through anexhaust port 25 controlled by piston 16. The timing of the opening andclosing of these ports, and their relative length (thus the durationduring which they are uncovered) may be varied in accordance with wellknown practice regarding engines of'this type, operating on thetwo-cycle principle.

Combustible charges are supplied from a carburetor 27 through an inletmanifold 28 which opens into an elongated transfer port or passage 34?.Details of a suitable carburetor are disclosed in said parentapplication.

Passage 3i? communicates with the inlet port 24 and with the spacesbehind each of the pistons 16 and 17. These spaces are closedrespectively by a finned head member 32- and a transverse partition 33,thus defining scavenging -pump chambers the volume of which is varied bydisr, placement of the respective pistons to draw in charges through acheck valve (not shown) in the carburetor when the pistons move towardeach other, and to pump charges through port 24 as the pistons separatedue to combustion of a charge in the space 20.

The movement of these pistons is exposed, in each case, by a biasingmember, and such member may conveniently be provided in the form of aspring 36 acting upon piston 16 and a spring 38 acting on piston 18,tending to drive the pistons toward each other and compressing chargesin the space 20. Other equivalent biasing means a may be provided ifdesired in place of these springs.

The pistons are shown in FIGS. 1 and 2 at approximately the outer limitsof their travel relative to the cylinder member ill, or in other Words,at the normal end of their power stroke resulting from combustion of acharge in space M). The springs 36 and 38 are thus shown essentiallyfully compressed, and it will be noted also that the pistons haveovertraveled the ports 24 and 25 to some extent. This arrangement ispreferred since it assures good breathing of the engine even when thereis a misfire or a sudden overload is placed on the engine.

Furthermore, it Will be noted that exhaust ports 25 are somewhat largerthan the intake ports, and the exhaust ports are so arranged that theynormally are uncovered first as the pistons separate on their powerstroke. A satisfactory arrangement has been obtained in this regard whenthe opening of the exhaust ports precedes opening of the intake ports byabout ten percent of the normal efiective travel of piston 16. Ampleintake area can be provided by increasing the number of intake portsaround the cylinder, and these ports can be directed at any desiredangle with reference to the cylinder axis, in accordance with knownpractice in the art of ported engines operating on the two-cycleprinciple.

An output rod 40 is secured to piston 16 and extends forwardly of thebody it? through baflle 33, extending through a seal bushing 41 therein.Similarly, an output rod 42 is fastened to piston 18 and extends throughpiston '16, having a seal therewith as by suitable sealing rings or thelike (not shown), and thence through the battle 33, through a sealbushing 43 at this point. The rods 49 and 42 carry respectiveregistration racks 45 and 46, and these racks in turn mesh with a commonpinion 43 which is mounted free to rotate upon a cross shaft 49 withinthe forward chamber of the body. This rack and pinion constructionnormally does not serve to transfer any power, but merely acts tomaintain proper relative movement and registry between the pistons 16and 18.

Mounted over the forward chamber of the body is a fuel supply tank 59inciuding filler tube 51 closed by a cap 52. The tank is supportedspaced from the chamber on straps 53, to minimize heat transfer to thetank. Fuel for forming combustible charges is transferred from this tankthrough supply pipe 54 to carburetor 27 Connected to the rods 4% and 42through the racks 45 and 46, and also providing a suitable mounting forsuch racks, are the reciprocating output or driving members 5-6 and 58which are thus directly coupled to the pistons 16 and 18, respectively.These members may be formed conveniently as complementarysemi-cylindrical rods which extend through a guide bearing 59 (FIG. 2)in the forward end of the housing, and it will be understood that thesemembers move parallel to each other but in oppositedirections, accordingto the movement of the corresponding pistons.

Bolted or otherwise secured to each of these output members are thecutting blades 60 and 62, secured respectively to the output members 56and 53. Thus, these lades will reciprocate parallel to each other, butin opposite directions, as the pistons 16 and 18 reciprocate, and thecutting teeth will therefore function accordingly. In order to maintainthese blades parallel and closely together, as desired, a suitableguiding mechanism is incorporated therewithin, the blades being groovedor notched as shown at 63 to produce a chamber of appro priate lengthinternally of (i.e., between) the blades 60 and 62. The blade 62 has aguide part 65 fastened thereto and including reversely curved endsforming gibs 66. These ends are received in U-shaped guide members ortracks 68 which are fastened to blade 69 in any suitable manner. Thus,the parts 66 slide within the members 68 and provide guides which holdthe blades in closely aligned and parallel position during operationthereof.

The operation of a portable saw constructed in accord- I ance with theinvention can be understood by reference to H68. 5 and 6 of the drawing.Fuel is supplied from tank 59 to the carburetor 27, and the combustiblemixture from the carburetor passes through intake manifold 28 to thetransfer passage 30. Assuming that the biasing springs 36 and 38 areeffective to move the pistons 16 and 18 respectively toward the centerof cylinder 15, "the clearance volume is indicated as the centralportion of the combustion space 26, at which point the ignition plug 22is located. In practice no particular stop mechanism is usually neededto maintain separation of the pistons at this time, since thecompression of the combustible mixture will resist the biasing force ofthe springs and maintain sufficient clearance volume. The combustiblemixture at this time is passing to the volumes behind the respectivepistons, into what may be conveniently termed scavenging pump chambers.

When the mixture is ignited between the pistons the resultant pressureof the expanding products of combustion will cause the pistons toseparate and will produce corresponding power output strokes of theblades 60 and 62, in the directions indicated in FIG. 6. As the pistonsseparate they of course act against the bias of the springs and willstore a certain amount of energy therein as well as supplying the powerto the cutting blades. The power so stored in the springs is returned inlarge measure to the engine system in producing the opposite orcompression stroke of the engine, and thus the action of the springs maybe considered analogous to that of the flywheel on a conventionalinternal combustion engine with a rotating crank shaft. When the pistonsseparate sufiiciently, piston 16 will first uncover the exhaust ports 25and the hot gases will commence to exhaust from the cylinder supplyahead of the uncovering or opening of the intake ports 24 by cylinder18. This general scheme of operation is known in the art, and issometimes referred to as a uniflow scavenging arrangement. Of course, atthis time the fresh charges of combustible mixture, having been drawninto the scavenging pump chambers behind the pistons upon thecompression stroke thereof, will be pumped out of such chambers throtwhthe transfer passage 30 and will enter the cylinder through the intakeports 24. A check valve is provided in the carburetor system to avoidreverse flow therethrough at this time, as is well known in the art, andas disclosed in detail in said copending application.

It was noted above that the springs 36 and 38 have a function similar toa flywheel. In addition to returning energy for purposes of moving thepistons in their compression stroke, some of the stored energy isapplied through the outputs 56 and 58 to the cutting blades, and theirreturn or opposite stroke, in the directions indicated in FIG. 5, isthus accomplished also under power. Thus, the present invention providesa compact, lightweight and efficient power saw apparatus wherein thedirect connection of reciprocating saw blades to the opposed pistonsaffords an efficient means for transferring energy from the opposedpistons of the engine directly to the cutting blades, with frictionlosses considerably reduced with respect to the normal type of rotaryengine drive and output. Moreover, by utilizing opposed pistonsconnected to oppositely moving reciprocating cutter blades, and bymaintaining the movement of the pistons in synchronism, as through therack and pinion registering mechanism disclosed, the masses of thepistons react in opposite directions and vibration of the apparatus isaccordingly minimized to a great extent, and reaction forces generatedby contact of the cutter blades against the material being out areessentially self-canceling.

The apparatus also is of minimum cross section, as will be apparentparticularly from inspection of the drawings, and thus is easilysupported and maneuvered by a single operator. The handles 12 and theirmounting straps can be rotated and fixed in any convenient positionaround the cylinder member, as can the fuel supply tank 50. If it'isfound necessary to maintain the carburetor in an upright position, ittoo can be mounted for adjustment about the cylinder, and a portion ofthe intake manifold 28 can be formed of flexible tubing to accommodatesuch movement of the carburetor. Therefore, the cutting edge of blades60 and 62 can be directed as desired with respect to the handles and theposition of the operator.

The invention also provides a novel arrangement for starting the engine.A fitting '74} (FIG. 2) incorporating a normally closed check valve (notshown) is mounted in the cylinder body adjacent ignition plug 22. Thisfitting provides a means for injecting gas under pressure, as from amanual air pump, into the combustion space to initiate movement of thepistons. If desired, such gas may be in the form of a combustiblemixture provided by adding a vaporized or atomized liquid fuel, or agaseous fuel such as propane, t0 the air from such pump. Details ofapparatus suitable for this purpose are disclosed in said parentapplication, and some of such apparatus is also shown in the embodimentof this invention illustrated in FIG. 10, as will presently bedescribed. If desired, in portable devices such as the saw justdescribed, the starting apparatus can be provided as a detachable unit.For example a quick-disconnect coupling can be incorporated in thefitting '70 to engage with an air pump during starting and then bedisconnected when the engine is running. Alternatively, the startingapparatus can be permanently attached as an inte ral part of the device.

FIG. 7 and FIG. 8 disclose modified forms of engine construction whichcan be used in accordance with the present invention. For purposes ofsimplification, only the essential elements of the engine are shown inschematic form, but it will be understood that the usual fuelair supplysystem may be provided, and suitable output connections can be made fromthe pistons, as will be described. Thus, referring to FIG. 7, thecylinder body 153:: is provided with opposed pistons 16a and 18a. Inthis particular arrangement, intake ports and exhaust ports arecontrolled by each piston, and thus for purposes of of explanation atthe top portion of the cylinder 1601, as shown in FIG. 7, the intakeports 24a are connected to the transfer passage 30a which in turnconnects to the scavenging pump chambers behind the pistons, and whichalso is connected to the combustible mixture supply device.

At the sides of the cylinder there are exhaust ports 25a, controlled byeach piston, and of slightly greater dimension than the intake portssuch that the exhaust ports are uncovered first by the moving pistonstoward the end of the power stroke. The output. connections are providedby the rods 43a and 42a, connected to the pistons 16a and Idarespectively. These rods may be connected to reciprocating cutter bladesor other apparatus to be driven in reciprocating fashion by the en-"gine, and the rack and pinion registry mechanism can be used in suchpower output connection. However, in some instances stable operation ofthe engine can be attained without the use of such registry mechanism,and it should be understood therefore that this mechanism is not anessential feature of the invention.

Similarly, with reference to FIG. 8, another form of engine inaccordance with the invention may include a' cylinder ltlb in whichpistons 16b and 18b operate in opposition, but wherein only one of thesepistons controls the intake and exhaust. Thus, for purposes ofexplanation the intake ports 24]; are shown adjacent the upper portionof the cylinder to be covered and uncovered by the piston 18]), andlikewise the exhaust ports 25b are formed at the same end of thecylinder to be controlled by piston 18b. In other respects, the engineis of the same general type, and functions in essentially the samemanner.

The present invention, while particularly applicable to light portablepower saws, also can be applied to the construction of other lightweightefficient cutting devices such as mowing machines having reciprocatingcutting blades. By way of example, FIGS. 9 and 10 show generally such amachine wherein a framework is provided including front legs 1% whichcarry a front axle 182 on which are mounted wheels 1103. Rear legs 104extend from the front legs of the framework, and are steadied by bracemembers 105. The rear legs support rear wheels 196.

The engine cylinder (FIG. 9) is mounted on brackets 112, these bracketsin turn extending from the framework,-and pistons 116 and 118 operatewithin the cylinder 110 in the same manner as the motors previouslydescribed. The springs 136 and 133 act against the respective pistons inthe same manner, and the output rods 14%) and 142 are connected toextension rods 143 and 144 zhich in turn may carry the registry controlracks 145 and 146, in mesh with the freely rotatable pinion 148. Rod 143is fastened at its lower or outer end to a lower clipper or cutter barres, and extension rod 144- is in turn suitably fastened to an upperclipper bar 162.

These clipper or cutter bars are mounted between stationary clamping orholder bars 165, and tensioning bolts 167, provided with suitableBelleville or spring washers 158, extend between the clamping bars andthrough guide slots in the cutter bars to maintain the cutter barsparallel and in close sliding relation. The bolts 167 can be adjusted toprovide the desired tension in the spring washers for determining theclamping force with which the cutter blades or bars are held together.

The handle 17d of the mowing machine preferably includes a tubularportion 172 within which a pump piston 173 operates under control of apump handle 175. This construction provides a simple starting air pumpwhich may be connected to the starter fitting 177 (FIG. 9) in cylinderlit for conducting starting gas under pressure into the engine. Asmentioned previously, further details 'of such a' starting system aredisclosed in said copending application.

The engine and cutting mechanism disclosed in FIGS.

9 and 10 operates on the same general principle as the previouslydescribed power saw apparatus. The pistons 116 and 118 separate underthe force of combustion of a charge in the cylinder, storing some energyin the springs 13$ and 138, and transferring some energy, to the cutterbars providing a cutting stroke. the exhaust and intake ports of theengine as described. On the return or compression stroke the energy fromthe springs is returned in part to the pistons for compressing a chargein the cylinder, and further energy is supplied from the springs to thecutter bars to produce power on the return stroke thereof.

While the forms of apparatus herein described constitute preferredembodiments of the invention, it is to be understood that the inventionis not limited to these precise forms of apparatus, and that changes maybe made therein 'without departing from the scope of the invention whichcombustible charges, means for introducing fresh charges into said spaceand for exhausting products of combustion from said space in timedrelation to movement of said piston, means for supplying a combustiblemixture to said charge introducing means including a fuel tank and acar- The pistons also control it to compress a combustible chargeintroduced into said space between said pistons while driving saidblades in a return stroke.

2. A self-contained reciprocating cutting device comprising a mainhousing, an engine cylinder formed in said housing, a pair of cuttingblades extending from one end of said housing and having cutting teethin side by side relation adapted to reciprocate in opposed paralleldirections producing a cutting action, a pair of opposed drive pistonsin said cylinder defining therebetween a space for combustion andexpansion of combustible charges, means for introducing fresh chargesinto said space and for exhausting products of combustion from saidspace in timed relation to movement of said pistons, means connectingone of said pistons to a corresponding one of said blades and the othersaid piston to the other said blades for concurrent movement thereofproducing opposed cutting movements of said blades in response tomovement of said pistons, energy storing means acting upon said pistonsin opposition to the force resulting from combustion of a charge in saidcylinder for storing energy and returning it to compress a combustiblecharge introduced into said space between said pistons while drivingsaid blades in a return stroke, and register means connected to saidpistons maintaining properly phased relative movement between saidpistons.

3. A portable self-contained power saw comprising a main housingincluding means for manual grasping to support and guide the saw, anengine cylinder formed in said housing, a pair of cutting bladesextending from one end of said housing and having cutting teeth in sideby side relation adapted to reciprocate in opposed parallel directionsproducing a cutting action, a pair of opposed drive pistons in saidcylinder defining therebetween a space for combustion and expansion ofcombustible charges, means for introducing fresh charges into said spaceand for exhausting products of combustion from said space in timedrelation to movement of said pistons, means connecting one of saidpistons to a corresponding one of said blades and the other of saidpistons to the other of said blades for concurrent movement thereofproducing opposed cutting movements of said blades in response tocombustion of charges in said space, means acting upon said pistons inopposition to the force resulting from combustion of a charge in saidcylinder tending to compress a combustible charge introduced into saidspace between said pistons and driving said blades in a return stroke.

4-. A portable self-contained power saw comprising a main housingincluding means for manual grasping to support and guide the saw, anengine cylinder formed in said housing, a pair of opposed drive pistonsin said cylinder defining therebetween a space for combustion andexpansion of combustible charges, means for introducing fresh chargesinto said space and for exhausting products of combustion from saidspace in timed relation to movement of said pistons, 21 pair of cuttingblades extending from one end of said housing and having cutting teethin side by side relation adapted to reciprocate in opposed paralleldirections producing a cutting action, means connecting one of saidpistons to a corresponding one of said blades and the other said pistonto the other said blade for concurrent movement thereof producingopposed cutting movements of said blades in response to movement of saidpistons from combustion of charges, energy storing means acting uponsaid pistons in opposition to the force resulting from combustion of acharge in said cylinder, and a register device correlating the movementof said pistons to maintain proper phase relation between said pistonsand the respectively driven cutting blades.

5. In a self-contained reciprocating cutting apparatus having a mainhousing, an engine cylinder formed in said housing, a pair of opposeddrive pistons in said cylinder defining therebetween a space forcombustion and expansion of combustible charges, a pair of coactingparallel cutting blades, one of said cutting blades connected to one ofsaid drive pistons and the other of said cutting blades connected to theother of said drive pistons for reciprocating movement therewith, meansfor introducing fresh charges into said space and for exhaustingproducts of combustion from said space in timed relation to movement ofsaid pistons, energy storing means acting upon said pistons inopposition to the force resulting from combustion of a charge in saidcylinder and for storing energy and returning it to compress acombustible charge introduced into said space between said pistons whiledriving said blades in a return stroke, and a starter including meansfor initially supplying a combustible charge under .pressure to saidspace acting to separate said pistons from their normal at restposition.

References Cited by the Examiner UNITED STATES PATENTS 1,349,698 8/20Tompkins.

2,244,215 6/41 Pescara.

2,330,937 10/43 Varis 92-65 X 2,598,480 5/52 Wright.

2,876,751 3/59 Kolthotf 123-46 2,904,022 9/59 MacDonald 123-46 2,912,96511/59 Campbell 123-46 3,023,563 3/62 Tenney 56-265 3,023,564 3/62 Tenneyet al 56-265 WILLIAM w. DYER, JR., Primary Examiner.

WALTER A. SCHEEL, DONALD R. SCHRAN,

Examiners.

1. A LIGHTWEIGHT PORTABLE, SELF-CONTAINED, RECIPROCATING CUTTING DEVICECOMPRISING A MAIN HOUSING HAVING MEANS FOR SUPPORTING AND GUIDING SAIDHOUSING, AN ENGINE CYLINDER FORMED IN SAID HOUSING, A PAIR OF CUTTINGBLADES EXTENDING FROM ONE SIDE OF SAID HOUSING AND HAVING CUTTING TEETHIN SIDE BY SIDE RELATION ADAPTED TO RECIPROCATE IN OPPOSED PARALLELDIRECTION PRODUCING A CUTTING ACTION, A PAIR OF OPPOSED DRIVE PISTONS INSAID CYLINDER DEFINING THEREBETWEEN A SPACE FOR COMBUSTION AND EXPANSIONOF COMBUSTIBLE CHARGES, MEANS FOR INTRODUCING FRESH CHARGES INTO SAIDSPACE AND FOR EXHAUSTING PRODUCTS OF COMBUSTION FROM SAID SPACE IN TIMEDRELATION TO MOVEMENT OF SAID PISTON, MEANS FOR SUPPLYING A COMBUSTIBLEMIXTURE TO SAID CHARGE INTRODUCING MEANS INCLUDING A FUEL TANK AND ACARBURETOR MOUNTED ON SAID HOUSING, MENAS CONNECTING ONE OF SAID PISTONSTO A CORRESPONDING ONE OF SAID BLADES AND THE OTHER SAID PISTON TO THEOTHER SAID BLADE FOR CONCURRENT MOVEMENT THEREOF PRODUCING OPPOSEDCUTTING MOVEMENT OF SAID BLADES IN RESPONSE TO MOVEMENT OF SAID PISTONS,AND ENERGY STORING MEANS ACTING UPON SAID PISTONS IN OPPOSITION TO THEFORCE RESULTING FROM COMBUSTION OF A CHARGE IN SAID CYLINDER FOR STORINGENERGY AND RETURNING IT TO COMPRESS A COMBUSTIBLE CHARGE INTRODUCED INTOSAID SPACE BETWEEN SAID PISTONS WHILE DRIVING SAID BLADES IN A RETURNSTROKE.